In-situ detection and analysis of methane in coal bed methane formations with spectrometers

ABSTRACT

A measuring system for in-situ measurements down a well ( 1 ) by a spectrometer ( 4 ) is provided. The spectrometer ( 4 ) includes a radiation source ( 5 ) and a detector ( 6 ). A probe ( 15 ) optically connected to the spectrometer ( 4 ) and includes an optical pathway ( 7 ) for transmission of a radiation from the radiation source ( 5 ) and at least a second optical pathway for transmission of a characteristic radiation from a sample to the detector ( 6 ). A positioner is provided to position the probe ( 15 ) near a side surface ( 11 ) of the borehole ( 3 ) and to optically couple the optical pathways ( 7 ) to the side surface ( 11 ), wherein the probe ( 15 ) is traversable up and down the well ( 1 ) by way of a guide operatively connected to the probe ( 15 ) and to a fixed location at the wellhead. By use of the apparatus and method a concentration of methane or other substance of interest is obtained, and thereby, a potential production of a coal bed methane formation is obtained.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/US01/11563, filed Apr. 11, 2001, designating the United Statesof America, and published as WO 01/77628, the entire disclosure of whichis incorporated herein by reference. Priority is claimed based onProvisional Application Nos. 60/196,620, 60/196,182, 60/196,523 and60/196,000 filed Apr. 11, 2000.

TECHNICAL FIELD

This invention relates to in-situ methods of measuring or analyzingdissolved, free, or embedded substances with a spectrometer and anapparatus to carry out the method. In particular this invention relatesto a method and apparatus of analyzing substances down a well. Moreparticularly, this invention relates to a method and apparatus todetect, analyze and measure methane or related substances in subsurfacecoal bed formations using a portable optical spectrometer to therebypredict a potential methane production of the well.

BACKGROUND AND SUMMARY OF THE INVENTION

Coal bed methane is methane that is found in coal seams. Methane is asignificant by-product of coalification, the process by which organicmatter becomes coal. Such methane may remain in the coal seam or it maymove out of the coal seam. If it remains in the coal seam, the methaneis typically immobilized on the coal face or in the coal pores and cleatsystem. Often the coal seams are at or near underground water oraquifers, and coal bed methane production is reliant on manipulation ofunderground water tables and levels. The underground water oftensaturates the coal seam where methane is found, and the undergroundwater is often saturated with methane. The methane may be found inaquifers in and around coal seams, whether as a free gas or in thewater, adsorbed to the coal or embedded in the coal itself.

Methane is a primary constituent of natural gas. Recovery of coal bedmethane can be an economic method for production of natural gas. Suchrecovery is now pursued in geologic basins around the world. However,every coal seam that produces coal bed methane has a unique set ofreservoir characteristics that determine its economic and technicalviability. And those characteristics typically exhibit considerablestratigraphic and lateral variability.

In coal seams, methane is predominantly stored as an immobile,molecularly adsorbed phase within micropores of the bulk coal material.The amount of methane stored in the coal is typically termed the gascontent.

Methods of coal bed methane recovery vary from basin to basin andoperator to operator. However, a typical recovery strategy is a well isdrilled to the coal seam, usually a few hundred to several thousand feetbelow the surface; casing is set to the seam and cemented in place inorder to isolate the water of the coal from that of surrounding strata;the coal is drilled and cleaned; a water pump and gas separation deviceis installed; and water is removed from the coal seam at a rateappropriate to reduce formation pressure, induce desorption of methanefrom the coal, and enable production of methane from the well.

Assessment of the economic and technical viability of drilling a coalbed methane well in a particular location in a particular coal seamrequires evaluation of a number of reservoir characteristics. Thosecharacteristics include the gas content and storage capability of thecoal; the percent gas saturation of the coal; the gas desorption rateand coal density, permeability, and permeability anisotropy; and gasrecovery factor.

While industry has developed methods to enhance production fromformations that exhibit poor physical characteristics such aspermeability and density, currently no practical methods are availableto increase the gas content of a coal seam. Thus, identifying coal seamsthat contain economic amounts of methane is a critical task for theindustry. The primary issue in identifying such coal seams involvesdeveloping a method and apparatus to quickly and accurately analyze coalseams for gas content.

Currently accepted methods of measuring gas content involve extracting asample of the coal from the seam and measuring the amount of gas thatsubsequently desorbs, either by volume or with a methane gas sensor.However, collection of the coal sample usually changes its gas contentto a significant extent before gas desorption is monitored. Thisdegradation of sample integrity leads to degradation of the datacollected. That degradation of data creates significant doubt in theresults of those common methods. As well, because these methods hinge onwaiting for the methane to desorb from the coal, they require inordinateamounts of time and expense before the data is available.

Downhole sensing of chemicals using optical spectroscopy is known foroil wells. For example, Smits et. al., “In-Situ Optical Fluid Analysisas an Aid to Wireline Formation Sampling”, 1993 SPE 26496, developed anultraviolet/visible spectrometer that could be placed in a drill string.That spectrometer was incorporated in a formation fluid sampling toolwhereby formation fluids could be flowed through the device and analyzedby the spectrometer. That spectrometer was largely insensitive tomolecular structure of the samples, although it was capable of measuringcolor of the liquids and a few vibrational bond resonances. The deviceonly differentiates between the O—H bond in water and the C—H bond inhydrocarbons and correlates the color of the analyte to predict thecomposition of the analyte. The composition obtained by the device isthe phase constituents of the water, gas and hydrocarbons. Bycorrelating observation of gas or not gas with observation of water,hydrocarbon, and/or crude oil, the instrument can distinguish betweenseparate phases, mixed phases, vertical size of phases, etc. Bycorrelating the gas, hydrocarbon, and crude oil indicators, theinstrument can presumably indicate if a hydrocarbon phase is gaseous,liquid, crude, or light hydrocarbon. A coal bed methane well withvarying hydrocarbons from coal to methane and, possibly, bacterialmaterial, provides an environment too complex for such a device todifferentiate methane and the other substances of interest. The deviceis not capable of resolving signals from different hydrocarbons to auseful extent, and the device is not capable of accurate measurementsneeded for coal bed methane wells. Furthermore, the requirements thatthe sample be fluid, that analysis occur via optical transmissionthrough the sample, and that the sample be examined internal to thedevice precludes its use for applications such as accurately measuringgas content of coal seams.

In other apparatuses known in U.S. Pat. No. 4,802,761 (Bowen et. al.)and U.S. Pat. No. 4,892,383 (Klainer, et. al.), a fiber optic probe ispositioned to transmit radiation to a chemically filtered cell volume.Fluid samples from the surrounding environment are drawn into the cellthrough a membrane or other filter. The fiber-optic probe then providesan optical pathway via which optical analysis of the sample volume canbe affected. In the method from Bowen et. al., a Raman spectrometer atthe wellhead is used to chemically analyze the samples via the fiberoptic probe. The method allows purification of downhole fluid samplesusing chromotographic filters and subsequent analysis of the fluid andits solutes using Raman spectroscopy. However, the stated requirementthat the Raman spectrometer be remote from the samples of interest andthat it employ fiber-optic transmission devices for excitation andcollection ensures that the sensitivity of the device is limited. Thedevice further does not consider the conditions present in subsurfacewells when analyzing the samples. Furthermore, as in the Smits et. al.case, the requirements in Bowen et. al. and Klainer et. al. that thesample be fluid and that the sample be examined internal to the devicesignificantly decrease the utility of the device for applications suchas measuring gas content of coal seams.

Methods of sample preparation and handling for well tools have beendescribed, as well. In U.S. Pat. No. 5,293,931 (Nichols et. al.), anapparatus is disclosed for isolating multiple zones of a well bore. Theisolation allows isolated pressure measurements through the well bore orwellhead collection of samples of fluids from various positions in thewellbore. However, such wellhead sample collection degrades sampleintegrity and does not provide a practical method or apparatus forassessment of gas content in coal seams. The apparatus shownsignificantly affects any sample collected and is basically a collectiondevice set down a well.

An object of the invention is to provide a method and system toaccurately measure substances in wells using optical analysis.

Another object of the invention is to provide a method and measuringsystem capable of measuring methane in a coal bed methane well.

Another object of the invention is to provide a method and measuringsystem which utilizes a spectrometer to analyze methane and othersubstances with emitted, reflected or scattered radiation from thesubstances and thereby allow a measurement of a side surface of thewell.

Another object of the invention is to provide a method and measuringsystem to accurately measure a concentration of methane in a coal bedmethane well and calculate a concentration versus depth for a singlewell and calculate concentrations versus depth for other wells tothereby predict a potential production of a coal bed methane field.

The objects are achieved by a measuring system for introduction into awell with a housing traversable up and down the well, a guide extendingdown the well from a fixed location and being operatively connected tothe housing, a spectrometer being located inside the housing andincluding a radiation source, a sample interface to transmit a radiationfrom the radiation source to a sample, and a detector to detect acharacteristic radiation emitted, reflected or scattered from the sampleand to output a signal, and a signal processor to process the signalfrom the detector and calculate a concentration of a substance in thesample.

Another aspect of the invention is a measuring system for in-situmeasurements down a well by a spectrometer. The spectrometer includes aradiation source and a detector. A probe is provided optically connectedto the spectrometer and including an optical pathway for transmission ofa radiation from the radiation source and at least a second opticalpathway for transmission of a characteristic radiation from a sample tothe detector. A positioner is provided to position the probe near a sidesurface of the borehole and to optically couple the optical pathways tothe side surface of the borehole, wherein the probe is traversable upand down the well by way of a guide operatively connected to the probeand to a fixed location at the wellhead.

Another aspect of the invention is a method of measuring methane in atleast one coal bed methane well. An instrument package is provided in ahousing, and the housing is lowered a distance down the well. Aradiation source is positioned to irradiate a sample, and a detector ispositioned to detect the characteristic radiation from the interactionbetween the sample and the incident radiation from the radiation source.The sample is irradiated to produce the characteristic radiation. Theconcentration of methane in the sample is measured by detecting thecharacteristic radiation with the detector. The detector transmits asignal representative of the concentration of methane to a signalprocessor, and the signal processor processes the signal to calculatethe concentration of methane in the sample.

In another aspect of the invention, a method of measuring a side surfaceof a borehole using optical spectrometers is provided. An opticalspectrometer with a radiation source and a detector is provided. Theside surface of the borehole is optically connected to the radiationsource and the detector. The radiation source irradiates the sidesurface of the borehole, and the emitted, reflected or scatteredcharacteristic radiation from the side surface of the borehole iscollected. The collected characteristic radiation is transmitted to thedetector to output or produce a signal. The signal is transmitted to asignal processor and the concentration of a substance on the sidesurface of the borehole is calculated.

The side surface is usually a solid material such as coal, sandstone,clay or other deposit. The side surface has been affected by the drillbit. The side surface may also have a film of drilling “mud” or someother contaminant (introduced or naturally found) that has beendistributed by the drill bit. The measurement system analyzes thesurface of that material, or the material is penetrated to analyze itsinterior. The surface may be treated (i.e. by washing it with water)before being analyzed. The material of interest is characterized alongwith any other materials adsorbed or absorbed to the material. Thesecould include gases, liquids, or solids. Preferably, the methaneadsorbed to the coal surface and in its pores is identified. The amountof methane on the surface and in the pores is measured.

The samples of interest may be a face of the coal seam, the coal itself,a bacterium or bacterial community which may indicate methane, the waterin the well, methane entrained in the coal or water, methane dissolvedin the water, or free gas. A free gas may be examined in-situ byproviding a pressure change to the water or to the coal and collectingthe resultant gas by way of a head-space. The sample or substance ofinterest may be physically, biologically or chemically treated in-situbefore measuring to enhance detection or measurement.

The radiation source is of particular concern and is selected dependingon the well environment, the substance to be measured and the backgroundof the sample. Coal shows inordinate fluorescence, and often bacteriaand other organic material are present near the coal seams. Thesesubstances tend to produce fluorescence which interferes withmeasurements of other substances. Upless the fluorescence is measured,the radiation source and wavelength are selected to minimize theseeffects. Coal tends to fluoresce between 600 nm and 900 nm with asignificant drop in fluorescence under 600 nm. A radiation source whichtakes into account these ranges is preferred for measuring the methane,especially the methane adsorbed to or embedded in the coal. Thus, themethane signature relative to the other components is maximized. In someinstances a signature of the fluorescence is maximized to characterizethe methane indirectly.

The measurements lead to establishing a concentration of methane in thecoal bed formation and to the potential production or capacity of thecoal bed. The methane is analyzed by obtaining through spectrometers aseries of spectra representative of scattered, emitted or reflectedradiation from methane in the well. The captured spectra are used todetermine the concentration at varying depths of methane present in thecoal bed formation. The spectra are manipulated and analyzed to producethe concentrations of methane represented in the well. The use offilters which are designed to eliminate or reduce radiation from sourcespresent in the well is needed to accurately determine the methaneconcentration or other parameters of the coal bed methane well. Otherparameters may include a predictor element or compound that is naturalor introduced to the coal bed or well. The filters are chosen dependingon the chemical which is of interest. Raman spectrometers are used inmost testing, however, near infrared lasers and detectors may beemployed to avoid the difficulties associated with fluorescence frommaterial or substances in the water or well. The measuring system inthis invention is based on high sensitivity. One factor that is used tomaintain high sensitivity of the system is the reduction or eliminationof moving parts throughout the measuring system.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side plan view of an embodiment of the invention and acoal bed methane well with the spectrometer located at the wellhead andtransmission of optical radiation using fibers to a downhole probe;

FIG. 2 shows a side plan view of another embodiment of the invention anda coal bed methane well with the spectrometer located in a housinglowered down the well;

FIG. 3 shows a sectional view of an embodiment of the housing with aflow passage for liquid or gas analysis;

FIG. 4 shows a sectional view of an embodiment of the housing with anon-contacting sample interface;

FIG. 5 shows a sectional view of an embodiment of the housing with ahead-space for gas analysis;

FIG. 6 shows a sectional view of an embodiment of the housing with anoff axis sample interface pressing to a side of the borehole;

FIG. 7 shows a sectional view of an embodiment of the probe with a fiberoptics;

FIG. 8 shows a sectional view of an embodiment of the probe with asample interface pressed against the side of the borehole;

FIG. 9 shows a sectional view of an embodiment of the probe with thespectrometer located downhole and a sample interface as a fiber-opticbundle pressed against the side of the borehole;

FIG. 10 shows a sectional view of an embodiment of the probe with a flowpassage and fiber-optic tip as the sample interface; and

FIG. 11 shows a sectional view of an embodiment of the probe with afiber-optic optical pathway.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a coal bed methane well 1 with a borehole 3 extending froma well head to a coal seam 10 with an aquifer fed water level 9. Thespectrometer 4 is located at or near the wellhead and includes aradiation source 5 for producing a radiation to transmit down theborehole 3 to a sample interface 25. The radiation from the radiationsource is transmitted by way of at least one optical pathway 7. Thesample, in this case being water, interacts with the radiationtransmitted from the radiation source 5, and a characteristic radiationfor the sample is produced by the interaction. The characteristicradiation is then transmitted by an optical pathway 7 to a detector 6located in the spectrometer 4 at the surface. A suitable optical pathway7 for transmission is optical fiber 8. Similar elements are representedby the same reference numeral in the drawings.

The optical fiber 8 extends down the borehole 3 to the housing 12 andfeeds into the housing through a high-pressure feed-through jacket 18.The jacket 18 allows the fiber 8 to enter the housing 12 withoutsubjecting the housing to the conditions down the well, such as highpressure, particles and the water. The housing protects any filter 14 orother instrumentation enclosed by the housing. The fiber 8 may extendout of the housing through another jacket 18 to optically couple thesample or substance of interest. A tip 15 of the fiber 8 supplies theradiation from the radiation source 5 and collects the characteristicradiation.

The optical fiber 8 may be a bundle of fibers where the center fibertransmits the radiation from the radiation source 5 and the other fiberstransmit the characteristic radiation. A single collection fiber for thecharacteristic radiation may also be used. The fiber 8 may also includea lens. The fibers use a polished tip or fused tip.

The sample interface includes an inlet 16 and an outlet 17 for the waterin the well. The water flows into the inlet when the housing ispositioned down the well at a depth and flows around the tip 15 of thefiber to thereby interact with the radiation from the radiation source5.

In a preferred embodiment shown in FIG. 2, the spectrometer 4 is locateddown the well 1 in a housing 12, thus reducing the effects of the longdistance transmission of the radiation. The spectrometer 4 is lowereddown the borehole 3 by a guide wire 21 to a depth, and the depth iscontrolled by a guide controller 20 at the surface 2.

This embodiment shows the radiation source 5 providing radiation by anoptical pathway 7 which is not a fiber. The radiation is directed to abeam splitter 23 and through a window 24 to interact with the sample orsubstance of interest. The emitted, reflected or scattered radiation isthen transmitted through the window 24 into the interior and through thebeam splitter 23 to the detector 6.

In this embodiment, no moving parts are present in the housing 12. Thisallows for increased sensitivity and accuracy.

The guide wire 21 may be a wireline, a slick line, coiled tubing, drillstem or other type of guide. The guide wire is provided for positioningthe housing down the well and may also transmit a signal to a datarecorder or other processor at the surface. If the signal is nottransmitted by the guide wire, a signal or data storage device is neededin the housing. The guide wire may also furnish electrical power to theinstrumentation located in the housing, or a battery may by located inthe housing.

FIGS. 3-6 show embodiments of the housing 12 with the spectrometer 4enclosed therein, when used with a guide wire 21. FIG. 3 shows a flowpassage for the sample interface where the radiation source 5 providesan incident radiation through a window 24 to interact with water. Thecharacteristic radiation is transmitted through another window 24 to thedetector 6. The characteristic radiation passes through filters 14before the detector 6. The housing 12 itself may be streamlined 26 toprovide for smooth passage of the housing down the well.

FIG. 4 shows a housing 12 designed for a non-contacting sample interfaceat the tip of the housing. Here the radiation source 5 producesradiation which is transmitted by an optical pathway 7 to a reflector orgrating 27 to direct the radiation through a window 24 at the tip of thehousing. The radiation interacts with the sample or substance ofinterest a distance away from the window 24. The characteristicradiation is then transmitted through the window 24 and to a reflectoror grating 27 to direct the characteristic radiation to the detector 6.

FIG. 5 shows a confocal arrangement for the housing 12. The radiationsource 5 provides radiation directed to a beam splitter 23 whichreflects the radiation to a lens 30 and through a window 24 into ahead-space 31. The characteristic radiation travels to the beam splitter23 and to another filter 14 and other lens 30 to the detector 6.

The sample interface includes the head-space 31 which entraps gasproduced by a depressurization of water in the flow passage. A plunger33 or other device is used to depressurize the water. The head-space 31collects the gas for measurement and analysis. Gates 32 are providedwhich allow the water to flow into the housing and then isolate thewater from the well to allow for depressurization.

FIG. 6 shows an off-axis spectrometer 4 configuration. The radiationsource 5 is off-axis from the well and face of the borehole 3. Theradiation source 5 provides a radiation down an optical pathway 7through a lens 30 and window 24 onto a sample or substance of interest.The characteristic radiation travels through the window 24, another lens30 and a filter 14 to the detector 6. The housing 12 has an adjustabledevice to press the housing to the side surface of the borehole. Anextendable leg 36 is provided that by a controller 37 moves out from thehousing 12 and contacts the side surface of the borehole opposite thewindow 24 and thereby moves the housing 12 towards the opposite side ofthe borehole. The confocal, off axis and non-contacting opticsarrangements may be interchanged.

FIGS. 7-11 show embodiments of the housings 12 where fiber optics 8 areemployed as at least a portion of the optical pathway 7. FIG. 7 shows ahousing 12 as a probe where the spectrometer is not located in thehousing. An optical fiber 8 supports the probe and positions the probealong the wellbore. A high-pressure feed-through jacket 18 is used toallow the fiber 8 to enter the housing 12 where filters 14 or otherdispersive elements are arranged. The fiber 8 exits the housing and thesample interface is a tip 15 of the fiber 8.

FIG. 8 shows the use of fiber 8 with an adjustable device for pressingthe sample interface against the side surface 11 of the wellbore. A bag40 is expanded by a controller 41 against the opposite side surface ofthe borehole to thereby press the tip 15 of the fiber 8 against or intothe side surface of the borehole.

FIG. 9 shows the use of fibers where the spectrometer 4 is located inthe housing 12. The radiation source 5 provides radiation to the fiber 8which transmits it to the sample by way of a jacket 18. A return fiber 8is adjacent or abutting the first fiber at the sample interface andextends through the jacket 18 to the detector 6. The housing 12 also hasan extendable leg 36 and controller 37 for pressing the housing 12 tothe side surface 11.

FIG. 10 shows a fiber optic extending down the well and entering ahousing 12 with a flow passage. A filter 14 or other dispersive elementsare enclosed in the housing 12 and protected from the well environment.The fiber-optic tip 15 protrudes through a jacket 18 into the flowpassage. The flow passage includes an inlet 16 with a filter 45 tofilter particulates and other entrained material in the water and anoutlet 17.

FIG. 11 shows a fiber 8 optical pathway which enters the housing 12 andprovides the transmitted radiation to a filter 14 or other dispersiveelement, lens 30 and window 24.

Optical spectrometers of utility for this method include, but are notlimited to, Raman spectrometers, Fourier Transform Raman spectrometers,infrared (IR) spectrometers, Fourier Transform infrared spectrometers,near and far infrared spectrometers, Fourier Transform near and farinfrared spectrometers, ultraviolet and visible absorptionspectrometers, fluorescence spectrometers, and X-Ray spectrometers. Allother spectroscopies which operate by observing the interactions and/orconsequences of the interactions between naturally-occurring,deliberately-induced, and/or accidentally-induced light and matter arealso of utility for this method.

For the spectrometer employing reflected, emitted or scatteredcharacteristic radiation, a Raman spectrometer, a near IR spectrometer,a IR spectrometer, a UV/Vis spectrometer or fluorimeter is suitable forcharacterizing the side surface of the borehole.

Previously, using spectrometers to measure dissolved methane in water orembedded methane at a remote location like a wellhead was not thoughtpossible. With the advent of portable and inexpensive yet highlyaccurate spectrometers, the measurement of dissolved methane in water ispossible. In some cases the spectrum used to analyze the material ofinterest may be obscured or blocked to some extent by the medium inwhich it is found. In the case of coal bed methane, the water andentrained particles may cause significant interference with anymeasurement of the dissolved or embedded methane. Certain steps may betaken to ensure a more accurate analysis of the methane.

Data correction, filters and steps to improve the signal of thespectrometer and methane may be used to accurately measure the methaneconcentrations. Methane has a characteristic peak or peaks in thescattered or returned optical spectrum. By adjusting filters and anydata correction equipment to the expected methane peak, the dissolvedmethane may be more accurately measured. Another way of correcting forthe interference of water or other entrained material is to adjust orselect the wavelength of the radiation used to decrease the effects ofthe water and entrained material and increase the returned signal due tothe methane. The wavelength may also be adjusted or selected toalleviate the effects of the length of the optical pathway. The lengthof the optical pathway from the spectrometer to the coal bed formationmay be 10,000 feet. The great length of pathway will result in increasederrors associated with the optical pathway. Means to adjust or correctthe laser radiation or returned radiation from the sample may beemployed at any location in the measurement system.

In an embodiment of this method, the spectrometers are physicallylocated outside of the water, while sampling probes are introduced intothe samples of interest. Such probes provide optical pathways via whichinteractions between light and matter are observed. In some cases, suchprobes also deliver the photons which interact with the matter. Theprobes used may have a lens to focus the source or characteristicradiation or filters to adjust the return spectrum radiation for anyflaws in the system or extraneous signals. The probes may need armoringor other means for protecting the probe due to the pressure and otherconditions of the well. The optical pathway or fiber optics may alsoneed protection from the conditions of the well.

When the probe is located extreme distances from the spectrometer, suchas down a well, corrections must be employed to correct for the inherenterrors due to the distance the source radiation and spectrum radiationmust travel. One way is to allow for longer periods of sampling in orderto receive several spectrums added together to analyze the methanepresent. Another way is to adjust the signal or radiation through afilter or correction device to allow correction feedback to adjust thereturn spectrum for flaws and errors associated with the radiationtraveling such distances.

In another embodiment of this method, the spectrometers are physicallyintroduced into the water so as to be near the samples of interest. Thismanifestation provides an unexpected benefit in that delivery of photonsto the samples and observation of interactions between light and matterare facilitated by the physical proximity of the spectrometers and thesamples.

Both embodiments may also use error correction devices such as darkcurrent subtractions of the return signal to correct for inherent systemnoise and errors. The systems may also use a technique of calibratingthe source radiation and spectrum signal to assure an accurate methaneconcentration measurement. Such techniques may include data processingfor comparing the signals to known spectrum signals. In order tocalculate the concentration of methane any of the known techniques ofcalculating the concentration from a spectrum may be used. A preferredmethod is partial least squares or PLS to calculate concentrations.

In order to realize a preferred embodiment of this method, it isnecessary to interface the spectrometers to the samples of interest.Interfacing the spectrometers and the samples can occur in several ways.Examples of those ways include, but are not limited to: direct opticalcoupling of the spectrometers and samples using light-guide devices;optical coupling of the spectrometers and chemicals which result fromphysically treating the samples; optically coupling of the spectrometersand chemicals which result from chemically treating the samples; andoptically coupling of the spectrometers and chemicals which result frombiologically treating the samples.

One manner of direct optical coupling of the spectrometers and samplesusing light-guide devices includes, but is not limited to, opticalcoupling of the interactions between light and matter via fiber opticdevices. This manifestation provides an unexpected benefit in thatdelivery of photons to the samples and observation of interactionsbetween light and matter occur with high throughput directly to thesamples in some cases.

A preferred manner of optical coupling is by way of direct transmissionof the radiation from the spectrometer to the sample via lenses, filtersand/or windows, and the direct transmission of the characteristicradiation from the sample to the detector by way of filters, windowsand/or lenses. This reduces the effects of long distance transmissionthrough fiber optics and facilitates the close proximity of aspectrometer and sample.

The filters used may be placed along the optical pathways of thespectrometer. The filters or dispersive elements, collectively filters,may be wavelength selectors, bandpass filters, notch filters, linearvariable filters, dispersive filters, gratings, prisms, transmissiongratings, echelle gratings, photoacoustic slits and apertures.

In order for the spectrometers to withstand the conditions particular towellbores, such as high pressure, low or high temperature, corrosiveliquids and dissolved solids, for example, it is preferable to enclosethe spectrometers in containers which protect them from such conditions.This novel method provides significant advantages over the prior art inthat the enclosed spectrometers can then be introduced directly into thewellbore. This method allows, but does not require, realization of thebenefit described by the direct interfacing or coupling of the samplesand spectrometers.

In order to interface the spectrometers and the samples using suchlight-guide devices in the wellbore, it is necessary to design theinterface in such a way that is suitable for the conditions particularto sampling environment, such as high pressure, low or high temperature,and dissolved solids, for example. The interface must withstand thoseand other conditions. One manifestation of such an interface for a fiberoptic probe includes, but is not limited to, a high pressurefeed-through jacket which interfaces between the conditions present inthe enclosed spectrometer and those present in the wellbore. Such ajacket provides significant advantages in that using such a jacketdirect optical coupling of the spectrometers to the samples becomespossible.

Methods of achieving optical coupling of the spectrometers and chemicalswhich result from physically treating samples includes, but is notlimited to, introduction of the samples into a portion of the enclosedspectrometers. That portion is then physically affected so thattreatment of the samples is achieved to give a chemical suitable for gasphase analysis via an optical pathway using one or more spectrometers.Such physical treatments include, but are not limited to,depressurization of the samples to release gas into a predefined

head-space

portion of the enclosure. That head space is then analyzed via opticalpathways using one or more of the spectrometers. This method provides anunexpected benefit in that gas-phase energy spectra of chemicals aretypically comprised of much higher resolution characteristics than thecorresponding liquid-phase spectra. Thus, delineation of complexmixtures of gases, such as methane and water, is facilitated using thismethod.

The water located in the coal bed formation is considered to be stableor at equilibrium. The drilling of the well may agitate the water andmay cause clouding or fouling of the water. In some circumstances theeffects of the drilling and preparation of the well may be toartificially effect the concentration of the methane in the water andsurrounding coal formations. Ways to correct the analyzed water may beemployed to more accurately reflect the true methane concentration ofthe formation at equilibrium. A simple way is to allow the well to comeback to an equilibrium after drilling or disturbance. Also, the probe orinstrument package that contacts the water in the coal bed formation maybe streamlined or controlled to allow for a smooth traverse in thewater. The locations of measurement in the well may also alleviate theeffects of destabilized water/methane concentrations. By analyzing thewater at the top of the formation first, and then continue withmeasurements down the well will effect the water equilibrium less whenmeasured before traversing the probe or package in the water to beanalyzed. A filter may also be used to strain the water or sample.

In order to accurately predict the capacity and the production of a coalbed methane formation by optical analysis, the well must be drilled toan appropriate depth. The depth of the water table, if present, thedepth of the top of the coal seam and the bottom of the coal seam arerecorded. The well head must be prepared to receive the probe orinstrument package. The probe must be coupled to the fiber-optic cable.The fiber-optic cable is coupled to the spectrometer that contains thelight source, dispersion element, detector and signal processingequipment and ancillary devices. The computer that serves as aninstrument controller, data collection and manipulation device isconnected to the spectrometer system. The system (computer,spectrometer, detector and laser) are powered and the laser andoperation equipment are allowed to reach an operating temperature. Thedetector is then cooled to operating temperature. The probe orinstrument package is lowered into the well through the well head untilthe probe or package reaches the water table. The source or laser emitsa radiation and the radiation is directed into the optical pathway orfiber-optic cable. The fiber-optic cable transmits the radiation downthe well to the probe. The probe emits the radiation onto the sample ofinterest. The probe may contain a lens or lenses to focus the radiationonto the sample at different distances from the probe. The radiationinteracts with the sample and causes the sample to reflect, scatter oremit a signature or characteristic radiation or spectrum. The spectrumor characteristic radiation is transmitted through the probe and opticalpathway to the spectrometer. The spectrometer detects the spectrum orcharacteristic radiation and analyzes the spectrum for characteristicmethane peaks or peak. The spectrometer then outputs information to thedata processor to be manipulated into information to be used tocalculate the concentration and potential production of methane.

During the analysis an initial spectrum is taken at the depth of thewater table. The fluorescence is measured and, if the fluorescence ishigh, the source radiation wavelength may be adjusted or selected tomitigate the fluorescence. If particulates are present and the noiselevel from them is high, a different focal length may be chosen tomitigate the noise level. The integration time for the detectors ischosen to maximize the signal. A dark current spectrum is taken with theshutter closed such that no light reaches the detector. The dark currentis the noise that is present in the system mostly due to thermaleffects. This intensity is subtracted from each spectrum to lower thenoise level. The number of co-additions is chosen to balance signal andtime constraints. The co-additions will improve the signal to noise butwill increase the time for each measurement. The probe or package islowered to the top of the coal seam and a spectrum is taken. The probeis again lowered and a spectrum is taken at regular intervals of depthuntil the bottom of the well is reached. The measurements show aconcentration of methane in accordance with depth in the well. Bycorrelating the concentration of methane in the well with other data,the capacity of the coal bed formation or seam can be calculated. Theprobe is then retracted and the well head sealed.

This embodiment of the invention details the technical detailssurrounding the use of three different optical spectrometer systemscapable of identifying and quantitatively analyzing coal bed methaneformations. This embodiment centers around development of an instrumentpackage capable of detecting the chemical signatures of dissolvedmethane and other gases in water and detecting embedded or trappedmethane in subsurface coal seams, both from a lowered instrument packageand from a fixed monitoring site. Such optic-based instruments aresuitable for complex analysis of the physical and chemical properties ofdissolved methane and similar formations in the wellbore environments.

In these cases, the instruments themselves are packaged and adapted tothe conditions prevalent in these environments, and the formations areexamined in the natural state or after suitable treatment. This providesdirect access to the chemistry and geology of the formations to anextent unavailable from core-sampling techniques.

At least three types of spectrometers are suitable for wellbore remotesensing of methane. The first two spectrometers, UV/Vis and near IR, areparticularly suitable for

head-space

sensing of gases released after depressurization of the coal bedsamples. UV/Vis spectroscopy provides data relating to the molecularabsorption properties of the water. Depending on experimental concerns,this data may contain information regarding the identity andconcentration of dissolved hydrocarbon gases. Regardless, though, itcontains information related to choosing the proper laser excitationwavelength for the Raman spectrometer. Near infrared (NIR) spectroscopyhas been widely used to remotely characterize complex gas mixtures. Inthis case, the NIR spectrometer provides data related to the structureand bonding of the gas samples. If the spectrometer resolution issufficient, that data contains sufficient information to allowdeconvolution of very complex samples.

Both of the above spectrometers require substantial fluid handling to beintegrated into the sensor or instrument package. This results in slowercollection times and, for the lowered instrument package, a lowerspatial resolution for the data, when compared to directly coupledin-situ methods. On the other hand, Raman spectroscopy is performedusing state-of-the-art high-pressure probes, allowing rapid chemicalanalysis of water and methane with no additional hardware.

Raman spectroscopy detects the identity and concentration of dissolvedhydrocarbon gases and embedded hydrocarbon gases. The Raman

scattering

of typical materials is quite low, producing significant signal-to-noiseproblems when using this type of spectroscopy. However, symmetricmolecules including methane show very strong scattering. This moderatessignal-to-noise concerns to some extent.

Again, all three spectrometers are refitted to suitable pressure tubespecifications. The tube-bound spectrometers will be immersed tosuitable depths on available well equipment or located adjacent thewell, and the data is collected using existing data translationprotocols. The data bandwidth for all three instruments is relativelylow

ca. 50 KB per minute is a reasonable rate (dependent to some extent onthe signal-to-noise concerns).

UV/Vis Spectrometer

Because UV/Vis spectrometers are based on low intensity, white lightsources, the use of focused optic probes (such as fiber optics) in thiscase is not appropriate. Such spectrometers are more suited to gasanalysis of the

head space

created after depressurization of a sample. Thus, in order to use theUV/Vis spectrometer for methane analysis, mechanized fluid controls arepreferred.

An automated fluid decompression chamber that can be filled,depressurized, analyzed, and evacuated on a continual basis at the welldepth of interest is provided. Depressurization of the chamber releasesthe dissolved hydrocarbon gases into the resultant vacuum where they areefficiently and quickly analyzed by the UV/Vis spectrometer. Evacuationand flushing of the chamber is followed by another cycle.

Some issues of concern using this type of spectrometer are developingthe appropriate optical path for analysis, avoiding fouling of thechamber and optical windows by water-borne chemicals and bio-organisms,and establishing the appropriate temperature/pressure conditions fordata collection. Corresponding solutions are multiple reflectioncollection geometries which afford very high sensitivities, properintroduction of anti-foulants to the chamber during flushing, andlaboratory correlation of the entire range of availablepressure/temperature collection conditions to resulting data quality.

Doing such head-space analysis also provides a convenient method for thesensor platform to analyze chemically gas bubbles resulting fromdissolution, cavitation or mixing, which would not otherwise be suitablefor analysis. For example, diversion of captured gas into the head-spacethrough appropriate valves provides the opportunity for direct UV/Visand NIR analysis of the emitted gases.

Near IR Spectrometer

Near IR and Raman spectrometers detect the identity (i.e. molecularbonding) and concentration of dissolved and embedded hydrocarbon gases.Near IR analysis, widely used for quality control in industrialprocesses, typically gives moderate signals with sufficient information(i.e. overtones of the vibrational bands) to treat very complicatedsamples. Near IR spectrometers may be used for head-space analysis.Allowing multiple reflections of the beam through the cell (and thusmultiple passes of the beam through the sample) provides the unexpectedbenefit of increasing the signal-to-noise ratio of the data. Directoptical coupling of near IR spectrometers to the samples is alsopreferred.

Raman Spectrometer

Raman spectroscopy is widely used for in-situ analysis of water-bornesamples because water does not have a strong interaction with typicalRaman laser energies. The Raman spectrometer is based on traditionalgrating optics, and thus enjoys a high throughput of light.

Spectroscopic capabilities are maximized by, in some cases, using afiber-optic probe sampling motif based around a filtered, six-around-onefiber-optic probe. The six-around-one fiber-optic probe allows for asafe, fully-sealed optical feed-through from the pressure vessel to thewater. This design removes the elaborate fluidics necessary for theother two spectrometers.

Until recently Raman spectroscopy would never have been considered as anin-situ probe due to the large size of available Raman systems and theirhigh power consumption. High efficiency diode lasers and charge-coupleddevice (CCD) detection, along with better filter technology have made itpossible to miniaturize Raman spectrometers and decrease powerconsumption. Fiber-optic probes have eliminated the complex samplingarrangements that once made Raman spectroscopy difficult and tedious.

A long output wavelength often provides useful spectra from samples thatproduce interfering fluorescence at lower wavelengths. Even at theselonger wavelengths, inorganic vibration shifts that are commonly 400 to1000 cm-1 wave numbers shifted in wavelength are still near the peaksensitivity of CCD detectors but with the added advantage of asignificant reduction in the background fluorescence interferencepresent in many samples. A preferred embodiment uses laser wavelengthswhich avoid to a reasonable extent any fluorescence characteristic ofthe sample.

Usually fluorescence is mitigated by providing a laser with a wavelengthabove the fluorescence. In a preferred embodiment a wavelength of 450 nmto 580 nm is provided from a diode laser. This range is below thewavelength of fluorescence of coal. The shorter wavelength is used todecrease the radiation from the coal and increase the relative radiationfrom the methane embedded or adsorbed on the coal.

Remote sampling is accomplished in some cases using a six-around-oneprobe. The epi-illumination probe incorporates one excitation and sixcollection fibers. This probe allows direct measurement of Raman ofdissolved hydrocarbons in water without having to transmit throughthick, non-quality optical window ports. High pressure feed-throughs areavailable for this probe.

Measurements of spectroscopic signatures of water-dissolved hydrocarbonsin the laboratory show an energy diagram of the known spectroscopicsignature regions of simple hydrocarbons, and the regions interrogatedby the three spectrometers considered herein. Thus, all threespectroscopies provide information relevant to the hydrocarbon identityand concentration.

However, the UV/Vis bands typical for these hydrocarbons are NOTstrongly characteristic

many compounds absorb in the energy region between 0 and 250 nm.Correlation of the UV/Vis results with those from the Raman and/or nearIR leads to detailed chemical analysis. As well, the UV spectrometermust operate in the region where the methane transition occurs.

The detectors used with the spectrometer system are important. To obtainhigh sensitivity and reduce interference from other substances a CCDtype detector is preferred. The charge-coupled device detector allowsfor only a small portion of the spectrum to be analyzed. Other detectorsinclude photomultiplier tubes, photo-diode arrays, CMOS image sensors,avalanche photo diodes and CIDs.

The measuring system may be supplied with power by the guide wires or byinternal batteries.

In order to predict or measure a potential production from a coal bedmethane field, a series of wells is measured. Taking measurements ofmethane or other substances of interest at a single well and at varyingdepths down the well provides a concentration of methane versus depthfor the well. This indicates the presence and amount of methane in thesubsurface zones or strata. By similarly measuring other wells in thecoal bed methane formation or field a dimensional plot of methane isobtained. From this the transport of methane, production zones andextent of methane bearing zones is obtained.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

We claim:
 1. A method of measuring methane using a spectrometer in acoal bed methane well with a borehole extending to at least a topsurface of at least one coal bed and containing water, comprising:providing a spectrometer including a radiation source and a detectorproviding a housing including a radiation source, a detector and asample interface, lowering the housing in the coal bed methane well to adepth down the well, positioning the sample interface to a samplelocated outside of the housing, irradiating the sample from theradiation source, detecting a characteristic radiation of the methanefrom the sample with the detector of the spectrometer, and processing asignal from the detector and spectrometer with a computer to calculate aconcentration of the methane.
 2. A method of measuring according toclaim 1, wherein the sample is a face of the coal bed.
 3. A method ofmeasuring according to claim 2, wherein the a radiation source isselected to minimize a radiation from the coal.
 4. A method of measuringaccording to claim 2, wherein a wavelength of the radiation source islower than a wavelength producing maximum fluorescence in the coal.
 5. Amethod of measuring according to claim 1, wherein the characteristicradiation is emitted, reflected or scattered radiation.
 6. A method ofmeasuring according to claim 1, wherein the sample is a volume of waterin the well at or near the depth down the well.
 7. A method of measuringaccording to claim 1, wherein the sample is a collected gas from thewater which has been depressurized to release the gas.
 8. A method ofmeasuring according to claim 1, wherein the sample is chemically treatedbefore the irradiating.
 9. A method of measuring according to claim 1,wherein the sample is biologically treated before the irradiating.
 10. Amethod of measuring according to claim 1, wherein the radiation sourceis selected to minimize fluorescence.
 11. A method of measuringaccording to claim 1, wherein the sample interface includes at least onelens to focus the radiation from the radiation source, and a focallength of the sample interface is adjusted to mitigate a noise level orto increase the detected characteristic radiation.
 12. A method ofmeasuring according to claim 1, wherein the radiation source is atunable laser located in the housing.
 13. A method of measuringaccording to claim 1, wherein the radiation source is a diode laser witha wavelength between 450 nm and 580 nm.
 14. A method of measuringaccording to claim 1, wherein the detector is an optical fibertransmitting the characteristic radiation to a charge-coupled device.15. A method of measuring methane in at least one coal bed methane well,comprising: providing an instrument package in a housing, lowering thepackage to a depth down the coal bed methane well, positioning aradiation source to irradiate a sample and a detector to detect acharacteristic radiation from the sample, irradiating the sample whichis located outside the housing with radiation from the radiation sourceto produce the characteristic radiation from the sample, and measuring aconcentration of methane in the sample by detecting the characteristicradiation from the sample with the detector, transmitting a signal fromthe detector to a signal processor and processing the signal tocalculate the concentration of the methane in the sample.
 16. A methodof measuring according to claim 15, wherein the radiation sourceincludes an optical fiber transmitting light waves from a spectrometernear a well head and connected to the housing.
 17. A method according toclaim 15, further comprising: lowering the package to at least a seconddepth down the well, and measuring a concentration of methane at thesecond depth, in order to obtain concentration of methane versus depthof the well.
 18. A method according to claim 15, further comprising:obtaining concentration of methane versus depth of at least a secondwell, in order to obtain a potential production of a coal formation. 19.A method according to claim 15, wherein the instrument package is sealedagainst water and armored to withstand pressure down the well.
 20. Amethod according to claim 15, wherein the package includes a radiationsource for supplying a radiation to irradiate the sample.
 21. A methodaccording to claim 15, wherein the package includes the detector fordetecting the characteristic radiation from the sample and transmittingthe signal.
 22. A method according to claim 21, wherein the packageincludes the signal processor for processing the signal from thedetector.
 23. A method according to claim 15, wherein the packageincludes a filter for filtering the radiation from the radiation source.24. A method according to claim 15, wherein the package includes afilter for filtering the characteristic radiation before the detector.25. A method according to claim 15, wherein the radiation source is adiode laser at a wavelength which minimizes a fluorescence of the coal.26. A method according to claim 15, wherein the depth is at a top of awater column in the well.
 27. A method according to claim 15, whereinthe depth is at a top of a first coal bed.
 28. A method according toclaim 15, wherein the depth is at a top of a second coal bed.
 29. Amethod according to claim 15, wherein the sample is water at or near thedepth.
 30. A method according to claim 15, wherein the sample is abacterium or bacterial community.
 31. A method according to claim 15,wherein the housing includes at least one window for transmitting theradiation from the radiation source and the characteristic radiation.32. A method according to claim 31, wherein the window is positionednext to the sample.
 33. A method according to claim 15, wherein thesample is a face of the wellbore.
 34. A method according to claim 33,wherein a portion of the housing is pressed into the face of thewellbore.
 35. A method according to claim 33, wherein the face of thewellbore is scraped or prepared to provide a sampling surface.
 36. Amethod according to claim 15, wherein the sample is a face of the coalbed.
 37. A method according to claim 15, further comprising selecting awavelength of the radiation source to mitigate fluorscence.
 38. A methodaccording to claim 37, wherein the wavelength is selected to mitigate aradiation from entrained particle in the water.
 39. A method accordingto claim 37, wherein the wavelength is selected to mitigate errors dueto length of optical pathways transmitting the radiation from theradiation source and the characteristic radiation.
 40. A measuringsystem for introduction into a well, comprising: a housing beingtraversable up and down the well, a guide extending down the well from afixed location and being operatively connected to the housing, aspectrometer being located inside the housing and including a radiationsource, a sample interface to transmit a radiation from the radiationsource to a sample located outside of the housing, and a detector todetect a characteristic radiation emitted, reflected or scattered fromthe sample and to output a signal, and a signal processor to process thesignal from the detector and calculate a concentration of a substance inthe sample.
 41. A measuring system according to claim 40, wherein theprobe has no moving parts.
 42. A measuring system for in-situmeasurements down a well with a borehole by a spectrometer, comprising:the spectrometer including a radiation source and a detector, a probebeing optically connected to the spectrometer and including an opticalpathway for transmission of a radiation from the radiation source and atleast a second optical pathway for transmission of a characteristicradiation from a sample to the detector, and a positioner to positionthe probe near a side surface of the borehole and to optically couplethe optical pathways to the side surface of the borehole sample, whereinthe sample is located outside of the probe, and wherein the probe istraversable up and down the well by way of a guide operatively connectedto the probe and to a fixed location at the wellhead.
 43. A measuringsystem according to claim 42, wherein the sample is methane adsorbed tocoal.
 44. A measuring system according to claim 42, wherein the opticalpathway for transmission of the radiation from the radiation sourceincludes at least one lens for focusing the radiation from the radiationsource onto the sample.
 45. A measuring system according to claim 42,wherein the positioner includes an adjustable device which extends fromthe probe and presses a side of the wellbore.
 46. A measuring systemaccording to claim 42, wherein the radiation source is a diode laser ata wavelength of 450 nm to 580nm.
 47. A measuring system according toclaim 42, wherein a filter is located between the radiation source andthe sample to filter the radiation from the radiation Source.
 48. Ameasuring system according to claim 42, wherein at least one filter islocated between the sample and the detector to filter the characteristicradiation.
 49. A measuring system according to claim 42, wherein theprobe includes the spectrometer.
 50. A measuring system according toclaim 49, wherein the probe is armored against pressure and sealedagainst liquids.
 51. A measuring system according to claim 49, whereinthe probe includes a high-pressure feed-through jacket for an opticalfiber which interfaces between the enclosed spectrometer and thewellbore.
 52. A measuring system according to claim 49, wherein theprobe includes a reflector to direct the radiation from the radiationsource to the sample and a second reflector to direct the characteristicradiation from the sample to the detector.
 53. A measuring systemaccording to claim 42, wherein an error corrector is provided to correctfor inherent system noise and errors.
 54. A measuring system accordingto claim 42, wherein the probe is optically connected to the radiationsource via at least one optical fiber.
 55. A measuring system accordingto claim 42, wherein the probe is optically connected to the detectorvia at least one optical fiber.
 56. A measuring system according toclaim 42, wherein the probe is streamlined so as not to substantiallydisturb the water in the well.
 57. A measuring system according to claim42, wherein the radiation source is a UV/Vis spectrometer.
 58. Ameasuring system according to claim 42, wherein the radiation source isa near IR spectrometer.
 59. A measuring system according to claim 42,wherein the radiation source is a Raman spectrometer.
 60. A measuringsystem according to claim 42, wherein the radiation source is aninfrared spectrometer.
 61. A measuring system according to claim 42,wherein the radiation source is a fluorimeter.
 62. A measuring systemaccording to claim 42, wherein the detector is a charge-coupled device.63. A measuring system according to claim 42, wherein the detectorincludes at least one of a photomultiplier tube, a photo-diode array, anavalanche photo-diode, a charge injection device and a complimentarymetal-oxide semiconductor image sensor.
 64. A method of measuring a sidesurface of a borehole using optical spectrometers, comprising: providingthe optical spectrometer including a radiation source and a detector,optically connecting the side surface of the borehole to the radiationsource and the detector, said side surface being located outside of thespectrometer, irradiating the side surface of the borehole withradiation from the radiation source, collecting a characteristicradiation emitted, reflected or scattered from an interaction betweenthe side surface of the borehole and the radiation from the radiationsource, transmitting the characteristic radiation to the detector tothereby produce a signal, transmitting the signal to a signal processor,and calculating a concentration of a substance on the side surface ofthe borehole.
 65. A method according to claim 64, wherein the sidesurface of the borehole is a face of a coal seam.
 66. A method accordingto claim 64, wherein the side surface is optically connected by at leastone lens which focuses the radiation from the radiation source onto theside surface.
 67. A method according to claim 64, wherein the sidesurface is optically connected to the radiation from the radiationsource by at least one fiber optic which is positioned near the sidesurface.
 68. A method according to claim 67, wherein the fiber optic ispressed into the side surface.
 69. A method according to claim 64,wherein the side surface is optically connected to the radiation fromthe radiation source via a window or lens in a housing.
 70. A methodaccording to claim 69, wherein the housing is pressed into the sidesurface.
 71. A method according to claim 69, wherein the housing islowered down the wellbore and is positioned near the side surface by anadjustable device extending from the housing.
 72. A method according toclaim 69, wherein the spectrometer is located in the housing.
 73. Amethod according to claim 64, wherein the radiation source is a diodelaser with a wavelength between 450 nm and 580 nm.
 74. A method ofanalyzing a coal bed methane reservoir comprising, providing aninstrument package in a well bore comprising a detector and spectrometerin a housing and measuring an amount of concentration of methane in thewell bore dissolved in a wellbore fluid with the detector andspectrometer to thereby predict the amount of the concentration ofmethane in the coal bed methane reservoir.
 75. A method according toclaim 74, wherein the amount measured is a concentration of methanedissolved in the wellbore fluid.
 76. A method of analyzing a coal bedmethane well having a borehole extending to at least a top surface of atleast one coal bed and containing water, comprising: providing ainstrument package comprising a detector and spectrometer in a housingin the well including a detector and a water sample interface in aborehole, positioning the sample interface to a sample located outsidethe housing, detecting a characteristic of a dissolved methane from thesample with the detector, and processing a signal from the detector by acomputer to calculate a concentration of the dissolved methane in thewater.
 77. A method according to claim 76, wherein the concentration ofdissolved methane predicts a production of the coal bed methane well.78. A method according to claim 77, wherein the production is an amountof methane contained within the coal bed methane reservoir.
 79. A methodaccording to claim 77, wherein the measurement instrument is an opticalspectrometer.
 80. A method of analyzing a coal bed methane reservoircomprising: (a) drilling a well with a well boring machine to anappropriate depth; (b) recording the depth of the water table ifpresent; (c) recording the depth of the top of the coal seam and thebottom of the coal seam; (d) preparing the well head to receive theprobe or instrument package; (e) coupling the probe to a fiber-opticcable; (f) coupling the fiber-optic cable to a spectrometer thatcontains a light source, dispersion element, detector and signalprocessing equipment and ancillary devices; (g) connecting thespectrometer system to a computer that serves as an instrumentcontroller, data collection and manipulation device; and (h) outputtinginformation from the spectrometer to the computer to be manipulated intoinformation to be used to calculate the concentration and potentialproduction of methane.
 81. A method of measuring methane in a coal bedmethane well with a borehole extending to at least a top surface of atleast one coal bed and containing water, comprising: providing aspectrometer, a detector and a sample located outside the housing in acoal bed methane well, irradiating the sample with the spectrometer,processing a signal from the detector to calculate a concentration ofthe methane in the water, and predicting a gas content of the coal bedusing a computer.
 82. A method of measuring according to claim 81,wherein the sample is a volume of water in the well at or near the depthdown the well.
 83. A method of measuring according to claim 81, whereinthe sample is a collected gas from the water which has beendepressurized to release the gas.
 84. A method of measuring methane inat least one coal bed methane well, comprising: providing an instrumentpackage in a well bore comprising a detector and spectrometer in ahousing, lowering the package to a depth down the well, measuring aconcentration of methane in a sample located outside the housing, andcalculating a concentration of the methane in the sample with a computerprocessor.
 85. A method according to claim 84, further comprising:lowering the package to at least a second depth down the well, andmeasuring a concentration of methane at the second depth, in order toobtain concentration of methane versus depth of the well.
 86. A methodaccording to claim 84, further comprising: obtaining a reservoircharacteristic of the well based upon the concentration.
 87. A methodaccording to claim 84, wherein the package includes a filter forfiltering the sample from particles in the well.
 88. A method accordingto claim 84, wherein the depth is at a top of a water column in thewell.
 89. A method according to claim 84, wherein the depth is at a topof a first coal bed.
 90. A method according to claim 84, wherein thesample is water at or near the depth.
 91. A method according to claim84, wherein the sample passes through a filter and is brought inside thehousing.
 92. A method according to claim 84, wherein the sample is a gasproduced from the water at or near the depth by depressurizing the waterinside the housing and collected in a head-space.